> How to use Mono.Unix or Mono.Unix.Native to check whether a specific
> system username and password are valid?
To write software that will run on all platforms, you can not really
check if a username/password are valid, because in Linux authentication
is done with a system called PAM (and GSSAPI).
At least in PAM's case, you might not even have a password, it might
authenticate using a fingerprint reading device, or it could use
one-time-passwords. So you really need to go through that process.
Miguel.